Drafting machine



p 1946- L. R. HALSTEAD DRAFTING"MACHINE I Fild oct'. 12, 1942 INVENTORZ'" L..1Zb/Zard//a5lazd,

Patented Sept. 10, 1946 DRAFTIN G MACHINE Laban Richard Halstead, Chicago, Ill., assignor to Eugene Dietzgen 00., Chicago, 111., a corporation of Delaware Application October 12, 1942, Serial No. 461,688

4 Claims. 1

The present invention relates in eneral to parallel motion apparatus and has more particular reference to drafting machines embodying parallel motion mechanism, the invention relating more especially to drafting apparatus adapted for attachment on a drawing board or table for the support of a ruling guide element, such as a straight edge, for movement within a drafting area on the board or table whilemaintaining the ruling element constantly at a selected angularity.

An important object of the invention is to provide parallel motion drafting apparatus in which the element supported for parallel movement is carried on jointed arm means including flexible belt means for maintaining the supported device in a desired angular position regardless of the movement of the supporting arm within the drafting area; a further object being toprovide simplified, inexpensive guard means for enclosing otherwise exposed portions of the flexible belt means.

Another important object is to form the guide support arm of parallel motion drafting apparatus by providing a pair of pulley carrying heads and extensible bar means, preferably a screw rod for supporting the heads in adjustably spaced relationship, to maintain a flexible endless belt at a desired tension on the pulleys, and to provide inexpensive, preferably sheet metal, channel members adapted for demountable assembly on said heads in position extending therebetween and enclcsingthe endless belt means between the heads; a further object being to form the spaced walls of the channel members with longitudinally extending beads therein for the purpose of strengthening the same against lateral bending whereby adequate strength may be had inchannels comprising lightweight sheet metal of minimum thickness. Another important object is to provide simplified means for mountin the opposed ends of a belt enclosing guard channel on the spaced pulley head of a parallel motion drafting machine; a, further object being to form the heads with grooves, notches or slots to interlockingly receive the ends of belt enclosing channels formed to lockingly fit the grooved portions of said slots; a further object being to utilize the inherent resilience of the sheet metal channels to hold the same inter-lockingly in the grooved pulley head slots, such construction and arrangement allowing the preformed channelmembers to be snapped into place and securely held in position on and extending between the spaced pulley heads.

Another important object is to provide simple and inexpensive belt covers for apparatus of the character mentioned, such covers serving not only to enclose the flexible pulley driving bands and thus guarding the operator of theapparatus against the danger of injury through sudden breakage of the band, but also serving generally to improve the appearanceof the apparatusand to impart additional rigidity in the pulley carrying arm of the drafting machine without, however, rendering the same absolutely rigid, a degree of flexibility being desirablein the arms of a parallel motiondrafting machine of the character mentioned.

The foregoing and numerous other important objects, advantages, and inherent functions of the invention will be fully understoodfrom the following description, which, taken in connection with the accompanying drawing, discloses a preferred embodiment of the invention.

Referring to the drawing:

Figure 1 is a perspective view of parallel motion mechanism embodying the present invention;

Figures 2 and 3 are sectional views, respectively, taken substantially along-the lines 2-2 and 3-3 in Figure 1;

Figure 4 is an enlarged sectional view taken substantially along the line 4-4 in Figure 2;

Figure 5 is a perspective view showing a channel member forming a part of the apparatus illustrated in Figures 1-4;

Figure 6 is a perspective view showing a modified channel end structure;

Figure '7 is a sectiona1 view illustrating the assembly of the structure shown in Figure 6; and

Figure 8 is a perspective view illustrating another channel end arrangement.

To illustrate the invention, the drawing shows parallel motion mechanism comprising means forming a pair of arm elements H and IS. The arms H and I; are preferably of substantially identical construction and may comprise each a pair of heads, the arm ll comprising spaced heads I5 and I1, and the arm l3 comprising spaced heads I9 and 2|.

These heads each comprise a rim 22, an embossment 24 extending radially outwardly of the rim, and a pair of projecting fingers 26 extending tangentially from the rim, the boss 24 and the projections 26 being parallel and extending in the same direction from the housing. The housings'forming the arm I l are maintained in spaced relationship by means of a spacing bar 21, the

opposite ends of which fit into sockets formed in the embossments 24 of the housings |5 and I1, an end of the bar 21 being in threaded con nection with the embossment 24 of at least one of said housings to allow the spaced relationship of the housings to be adjusted by turning the bar 21 with respect to the housings. The housings l9 and 2| forming the arm I3 are likewise supported adjustably in spaced apart relationship by means of a spacing bar which is preferably identical to the bar 21 The heads l5, I1, I 9 and 2| comprise pulley housings. The head |5 encloses a pulley fixed on a shaft or pin which extends below the housing, said pin being rigidly secured in a clamp bracket 23 by means of which the drafting machine may be anchored on a drafting board or table, as at the edge thereof, so that the arms I and I3 may be supported for movement over the drafting surface afforded by the board or table. Means is provided within the head l5 for supporting the same on and for rotary movement about the axis of the pin and the pulley carried by the pin Within the housing l5.

The housings I! and I9 cooperate to form an enclosure for a duplex pulley or double pulleys drivingly connected, as on a common shaft, one pulley being enclosed in the housing ll, while the other is enclosed in the housing I9, the pulleys being supported for rotation with respect to both housings whereby the housings Ill and I 3 are interconnected for relative rotation about the axis of the pulleys enclosed thereby.

The housing or head 2| also encloses a pulley supported for rotation therein, said pulley carrying a ruling guide 25 which preferably extends outwardly of the housing 2| at the under side thereof, the pulley in the housing 2| also carrying means including the manually operable knob 39 for adjusting the angularity of the guide 25 with respect to the pulley and for latching the guide in angularly adjusted position.

The pulleys in the housings I5 and I1 are drivingly connected by endless belt means and the pulleys in the housings l9 and 2| are likewise drivingly interconnected. The driving belt means in each arm preferably comprises an endless steel tape 28 riding in flat grooves formed in the spaced pulleys drivingly connected thereby, the belts extending from the pulley housing heads through channels formed in the projections 26. By manipulating the spacing bars and thus adjusting the spacement of the pulley carrying heads, the driving bands 23 may be placed under suitable tension in order to drivingly interconnect the pulleys whereby to maintain the same fixed angular relationship between the table and the pulley in the housing 2|, regardless of swinging movement of the arms H and 3 over the drafting surface. The belts, in other words, connect the pulley in housing 2|, through the pulleys in housings l1 and I9, to the pulley in housing l5 which is fixed to the drafting table. Thus the pulley in the housing 2| is held against turning with respect to the drafting surface while supported for swinging movement thereover by the linked arms II and I3.

In order to enclose and protect the driving belts 28 between the pulley heads, thereby improving the appearance of the drafting machine, and also bracing and rigidifying the arms I and I3 to some extent while guarding the operator of the machine against injury in the event of snapping of a belt 23 when under tension in service or through accidental over-tensioning, guard members 29 are provided. These guard members preferably comprise sheet metal channels having spaced side walls 3|, and may be formed from a single strip of sheet metal by bending the same along a medial line of bend to form a curved channel portion 33 interconnecting the sides of the channel. In order to strengthen the channel melnber, which is preferably formed of thin sheet metal of minimum thickness, the side walls are provided with longitudinally extending flutes 35, preferably pressed outwardly in the side walls 3| to form longitudinally extending beads. The projections 26 of the pulley housings are drilled longitudinally to form a circular opening 3'! therein extending from the extremity of the projection and opening into the pulley receiving cavity defined by the rim 22. After the circular opening has been drilled or otherwise formed in each of the projections 26 of the several heads, said projections may then be sawed or otherwise cut to form a preferably rectangular slot 39 extending in the projection diametrically with respect to the circular opening 31, the slot 39 being open along one side of the projection whereby the slot has a closed bottom. The slot is formed preferably so that the circular opening 31 extends midway between the bottom and open side of the slot 39.

The foregoing structure provides an open slot in each projection 26 having longitudinal grooves 38 in the sides of the slot-so that an end of the channel 29 may be received in the grooved slot with the flutes of the channel interlockingly engaged in the lateral slot grooves 38. A guard member 29, because of the resilience imparted by the curved portions 33 thereof, may be inserted through the open sides of the slots in aligned projections 26 of a pair of pulley heads by compressing the ends of the member 29 to allow the fluted portions 35 to pass through the open side of the slot and snap into place in the slot grooves 38. After assembly in such fashion, the inherent resilience of the member 29 will insure that the same remains latched in mounted position.

It will be seen that the channel member 29 may be applied in the slots of spaced fingers 26 with the curved top 33 of the channel uppermost, whether the slots open upwardly, as in the fingers 26 of the arm l3, or whether the slots open downwardly, as in the heads of the arm Consequently identical channels 29 may be used for both arms H and I3, and, moreover, the jigs and fixtures for slotting the projections 26 may be identical for all of the heads IE, IT, l9 and 2|.

While the guards 29 formed as shown in Figure 5 are entirely satisfactory for practicing the present invention in the manner described, it will be seen that, since the ends of the channels 29 are merely frictionally fitted in the slots 39, longitudial movement of the channel ends in the slotted projections 26 is allowed freely in either direction, limited only by engagement of the channel ends with the peripheral surfaces of the pulleys. The channels are sized so that neither end of the channel may be withdrawn axially from the end of its supporting projection 26. While no harm will result through engagement of the end of a channel 29 with the surface of the adjacent pulley, it is preferable, as a refinement, to form the channels with outwardly projecting embossments 4| adjacent the ends thereof, said embossments affording shoulders adapted, as shown in Figure 7, to engage the end of the housing projection 23 and thereby limit the movement of the channel end into the embossment at a point such as to prevent the end of the channel from engaging the periphery of the pulley.

I It will be noted that the embossment 4| li-mits movement of the channel end in one direction only in the housing projection 26, and it may be desirable in some instances to anchor at least one end of the channel in the housing projection in which the same is mounted. To this end, as shown in Figure 8, the channel, preferably in the grooved portion 35 thereof, may be formed with an outward embossment 43 of preferably hemispheric configuration, in position to snap into and engage in an opening 45 formed in the housing projection 26, such opening 45 preferably being formed by drilling through the housing projection 26 in a direction at right angles to the slot 39.

It will be seen from the foregoing that the fluted channels 29 afford an extremely simple and inexpensive means for enclosing the steel tapes 23 between the pulley housings forming the arms H and i3. These tape guarding channels 29 may be formed of extremely thin, inexpensive sheet metal and, to minimize manufacturing expense, the flutes 35 and the embossments 4| and 43 may be formed in the sheet metal strips, while the same are in flat condition. After forming the flutes 35 and the embossments M or 43, if desired, .the formed strip may then be bent along the line of bend 33 to provide the channel in finished condition ready for assembly in the drafting machine. When assembled, the channels not only serve to enclose the pulley driving tapes-2B, but also materially improve the superficial appearance of the drafting apparatus, and, furthermore, aid to some extent in rigidifying the arms I! and i3 by minimizing the tendency of one pulley head to turn, with respect to the other, about the axis of the spacing rod 21. The channels 29, however, do not impart absolute rigidity in the arms, for a limited amount of relative turning of the heads about the axis of the spacing rod is desirable in order to accommodate the supported ruling guide 23 to the drafting surface,

It is thought that the invention and its numerous attendant advantages will be fully understood from the foregoing description, and it is obvious that numerous changes may be made in the form, construction and arrangement of the several parts without departing from the spirit or scope of the invention, or sacrificing any of its attendant advantages, the form herein disclosed being a preferred embodiment for the purpose of illustrating the invention.

The invention is hereby claimed as follows:

1. In parallel motion apparatus comprising an arm having a pair of spaced heads, a turnable member in each head, a. driving member interconnecting said turnable members, said driving member including a portion extending between said heads, the combination of a detachable cover extending between and attached at its 015- posite ends on said spaced heads in position enclosing the driving member between said heads, said cover comprising a shell of resilient material having an end formed with a longitudinally extending flute and at least one of said heads having a socket formed with a longitudinal groove for receiving said flute to secure the end of said cover on said head, said cover having an embossment forming a, shoulder spaced from and facing the end of the cover in position to engage said head at the open end of the socket and limit longitudinal movement of the end of the cover inwardly in said socket.

2. In parallel motion apparatus comprising an arm having a pair of spaced heads, a turnable member in each head, a driving member interconnecting said turnable members, said driving member including a portion extending between said heads, the combination of a detachable cover extending between and attached at its opposite ends on said spaced heads in position enclosing the driving member between said heads, said cover comprising a resilient shell of sheet metal having a pair of spaced walls, at least one of which is formed with an outwardly pressed flute extending substantially throughout the length of the cover for strengthening the same, said flute being disposed between the opposite sides of the wall in which it is formed, said heads having each a socket for receiving the opposed ends of said cover, one of the said sockets comprising a lateral open slot having opposing walls and a closed bottom, and a longitudinal groove in a wall of the slot in position between the bottom and the open side of the slot, whereby the end of the cover may be assembled in the slot through said open side, by compressing the opposed walls of the cover, the resilience of which, after assembled, serves to yieldingly press the walls of the cover apart in said slot and interlock the flute in said groove to retain the cover in the slot.

3. The combination as set forth in claim 2 wherein said cover is formed with an embossment forming a shoulder spaced from and facing toward an end of the cover in position to engage the head at the open end of the socket thereof and limit longitudinal movement of the end of the cover inwardly of said socket.

4. The combination as set forth in claim 2 wherein at least one of said heads and the end of said cover received therein comprise cooperating latch members including a latching projection on one latch member and a cooperative cavity on the other for receiving said projection, whereby to latch the end of the cover in the socket of said head against relative movement of the cover with respect to the head in the direction of the interfitting flutes and grooves.

L. RICHARD HALSTEAD. 

